Sealing liquid for anodic oxide coating films of aluminum alloy, concentrated liquid and sealing method

ABSTRACT

The present invention provides a sealing treatment solution free from a nickel salt. The sealing treatment solution is capable of ensuring a sealing performance comparative to that in the method using a sealing treatment solution containing a nickel salt, and ensuring that the resulting sealing-treated anodic oxide film has excellent contamination resistance. The present invention provides a sealing treatment solution for anodic oxide film of aluminum alloy, the sealing treatment solution comprising a metal salt, a pH buffer, and a surfactant, the metal salt being at least one member selected from alkali metal salts and alkaline-earth metal salts.

TECHNICAL FIELD

The present invention relates to a sealing treatment solution for an anodic oxide film of aluminum alloy, a concentrated liquid, and a sealing treatment method.

BACKGROUND ART

Anodic oxide films of aluminum alloy are generally subjected to a sealing treatment for the purpose of preventing contamination, improving corrosion resistance, and the like. Examples of known sealing treatment methods include boiling water sealing, vapor sealing, normal temperature sealing, nickel acetate sealing using a nickel acetate aqueous solution, and the like (see Non-Patent Document 1).

Among these, nickel acetate sealing has particularly been preferred because of the easy assurance of corrosion resistance of the film compared with boiling water sealing, superior work efficiency compared with vapor sealing, and easy liquid management compared with normal temperature sealing, and the like.

However, due to recent concerns about nickel allergy or the toxicity of nickel salt fine powder, there has been a demand for the production of an anodic oxide film by a sealing treatment method that does not use a nickel salt but is capable of producing an anodic oxide film ensuring a corrosion resistance, sealing degree, and like sealing performance, comparable to that of nickel acetate sealing.

CITATION LIST Non-Patent Document

-   Non-Patent Document 1: The “metal salt sealing treatment” section in     Aluminum Hyomen-Gijyutsu Binran, (Aluminum Surface Technique     Handbook), edited by Light Metal Publishing Co., Ltd

SUMMARY OF INVENTION Technical Problem

The present invention was made in light of the problems of prior art described above, and an object of the present invention is to provide a sealing treatment solution free from nickel salt. The sealing treatment solution is capable of ensuring a sealing performance comparable to that of the method using a sealing treatment solution containing a nickel salt, and ensuring that the resulting sealing-treated anodic oxide film has excellent contamination resistance.

Solution to Problem

The present inventors have conducted extensive research to achieve the above object. As a result, the inventors found that the above problems can be solved by a sealing treatment solution for an anodic oxide film of aluminum alloy comprising a metal salt, a pH buffer, and a surfactant; the metal salt is at least one member selected from alkali metal salts and alkaline-earth metal salts. With this finding, the inventors completed the present invention.

Specifically, the present invention relates to a sealing treatment solution for an anodic oxide film of aluminum alloy, a concentrated liquid, and a sealing treatment method, as detailed below.

1. A sealing treatment solution for anodic oxide film of aluminum alloy, the sealing treatment solution comprising a metal salt, a pH buffer, and a surfactant, the metal salt being at least one member selected from the group consisting of alkali metal salts and alkaline-earth metal salts. 2. The sealing treatment solution according to Item 1, wherein the metal salt is a metal salt of at least one metal selected from the group consisting of Na, Mg, K and Ca. 3. The sealing treatment solution according to Item 1, wherein the metal salt is a metal salt of at least one metal selected from the group consisting of Mg and Ca. 4. The sealing treatment solution according to any one of Items 1 to 3, wherein the metal salt is at least one member selected from the group consisting of acetates, sulfamates, sulfates, and nitrates. 5. The sealing treatment solution according to any one of Items 1 to 3, wherein the metal salt is a nitrate. 6. The sealing treatment solution according to any one of Items 1 to 5, wherein the pH buffer is at least one member selected from the group consisting of organic acid salts, ammonium salts, amino acids, borates, amine compounds, and nitrogen-containing heterocyclic compounds. 7. The sealing treatment solution according to any one of Items 1 to 5, wherein the pH buffer is a nitrogen-containing heterocyclic compound. 8. The sealing treatment solution according to any one of Items 1 to 7, wherein the surfactant is at least one member selected from the group consisting of anionic surfactants and ampholytic surfactants. 9. The sealing treatment solution according to any one of Items 1 to 7, wherein the surfactant is at least one member selected from the group consisting of sulfate-based surfactants, sulfonate-based surfactants, and phosphoric ester-based surfactants. 10. The sealing treatment solution according to any one of Items 1 to 9, wherein the sealing treatment solution has a pH of 7.0 to 10.0. 11. The sealing treatment solution according to any one of Items 1 to 10, wherein the sealing treatment solution is free from nickel-based metal salt. 12. The sealing treatment solution according to any one of Items 1 to 11, wherein the total amount of the metal salt, the pH buffer, and the surfactant in the sealing treatment solution is 0.2 to 100 g/L. 13. A concentrated liquid of a sealing treatment solution for anodic oxide film of aluminum alloy, the sealing treatment solution comprising a metal salt, a pH buffer, and a surfactant, the metal salt being at least one member selected from the group consisting of alkali metal salts and alkaline-earth metal salts. 14. A sealing treatment method for an anodic oxide film of aluminum alloy, comprising the step of:

-   -   immersing an article having an anodic oxide film of aluminum         alloy in a sealing treatment solution for an anodic oxide film         of aluminum alloy,     -   the sealing treatment solution comprising a metal salt, a pH         buffer, and a surfactant, and     -   the metal salt being at least one member selected from the group         consisting of alkali metal salts and alkaline-earth metal salts.         15. The sealing treatment method according to Item 14, wherein         the sealing treatment solution has a liquid temperature of 85 to         100° C.         16. The sealing treatment method according to Item 14 or 15,         wherein the sealing treatment solution has a pH of 7.0 to 10.0.         17. An article sealed by the sealing treatment method according         to any one of Items 14 to 16.

Advantageous Effects of Invention

The sealing treatment solution of the present invention makes it possible to impart a sealing performance comparable to that in the method using a sealing treatment solution containing a nickel salt, and impart superior contamination resistance to an anodic oxide film of aluminum alloy.

Further, the concentrated liquid of the present invention makes it possible to easily prepare the aluminum alloy anodic oxide film sealing treatment solution of the present invention by simply diluting the concentrated liquid.

The sealing treatment method for an anodic oxide film of aluminum alloy of the present invention makes it possible to impart a sealing performance comparable to that of the method using a sealing treatment solution containing a nickel salt, and impart superior contamination resistance to an anodic oxide film of aluminum alloy.

DESCRIPTION OF EMBODIMENTS

The present invention is specifically explained below.

1. Sealing Treatment Solution

The sealing treatment solution of the present invention is a sealing treatment solution for an anodic oxide film of aluminum alloy, comprising a metal salt, a pH buffer, and a surfactant. The metal salt is at least one member selected from alkali metal salts and alkaline-earth metal salts.

Metal Salts

The metal salt contained in the sealing treatment solution of the present invention is at least one member selected from the group consisting of alkali metal salts and alkaline-earth metal salts. Examples of alkali metal salts and alkaline-earth metal salts include, but are not particularly limited to, preferably, water-soluble salts, such as carboxylates, sulfamates, sulfates, nitrates, organic sulfonates, and the like. Among them, in terms of obtaining a sealing-treated anodic oxide film of aluminum alloy having excellent contamination resistance, carboxylate, sulfamates, sulfates, and nitrates are more preferable; acetates, sulfamates, sulfates, and nitrates are still more preferable; acetates and nitrates are furthermore preferable; and nitrates are particularly preferable. The metal salts may be used alone or as a mixture of two or more salts.

The metal contained in the metal salt is not particularly limited insofar as it is an alkali metal or an alkaline-earth metal; specifically, Li, Be, Na, Mg, K, Ca, Rb, Sr, Cs, Ba, Fr, and Ra may be used. Among them, in terms of obtaining a sealing-treated anodic oxide film of aluminum alloy having excellent contamination resistance, metal salts of Na, Mg, K, and Ca are preferable; metal salts of Mg and Ca are more preferable; and metal salts of Mg are furthermore preferable. The metals contained in the metal salts may be used alone or as a mixture of two or more metals.

The concentration of the metal salt or salts in the sealing treatment solution is not particularly limited, and is preferably 0.001 to 1 mol/L, and more preferably 0.01 to 0.5 mol/L. The above range of metal salt concentration enables the sealing treatment solution to exert a sufficient sealing performance, thereby enabling the anodic oxide film of aluminum alloy treated by the sealing treatment solution to sufficiently exert a contamination resistance.

pH Buffer

The pH buffer is not particularly limited, and various known pH buffers may be used. Examples of the pH buffer include organic acid salts, ammonium salts, amino acids, borates, amine compounds, nitrogen-containing heterocyclic compounds, and the like. Among these, nitrogen-containing heterocyclic compounds are preferable in terms of imparting superior contamination resistance to an anodic oxide film of aluminum alloy sealed by the sealing treatment solution.

Examples of organic acid salts include salts of carboxylic acid and oxycarboxylic acid. The carbon numbers of the carboxylic acid and the oxycarboxylic acid are preferably 4 or less. Examples of the salts include sodium salts and potassium salts.

Examples of ammonium salts include ammonium salts of organic and inorganic acids. Examples of ammonium salts of organic acids include ammonium salts of carboxylic acid and oxycarboxylic acid. The carbon numbers of the carboxylic acid and the oxycarboxylic acid are preferably 4 or less. Examples of ammonium salts of inorganic acids include ammonium sulfates, ammonium nitrates, ammonium sulfamates, and the like.

Examples of amino acids include glycine, alanine, asparagine, and their salts. Examples of borates include sodium borate, potassium borate, ammonium borate, and the like. Examples of amine compounds include ethanolamines, i.e., monoethanolamine, diethanolamine, and triethanolamine. Examples also include alkylamines, aromatic amines, urea, and like water-soluble carbonyl amines.

Examples of nitrogen-containing heterocyclic compounds include heterocyclic compounds containing at least one nitrogen atom as a heteroatom, and heterocyclic compounds containing at least one nitrogen atom and at least one oxygen atom as heteroatoms.

Examples of nitrogen-containing heterocyclic compounds include nitrogen-containing heterocyclic compounds containing an ethylenimine ring, an azirine ring, an azetidine ring, an azete ring, a pyrrolidine ring, a pyrrole ring, a piperidine ring, a pyridine ring, a hexamethyleneimine ring, an azatropilidene ring, an imidazole ring, a pyrazole ring, an oxazole ring, an imidazoline ring, a pyrazine ring, a morpholine ring, a pteridine ring, a purine ring, and the like. Among these, nitrogen-containing heterocyclic compounds containing a pyrrolidine ring, a pyrrole ring, a piperidine ring, a pyridine ring, a hexamethyleneimine ring, an azatropilidene ring, an imidazole ring, a pyrazole ring, an oxazole ring, an imidazoline ring, a pyrazine ring, a morpholine ring, a pteridine ring, a purine ring, and the like are preferable.

Examples of nitrogen-containing heterocyclic compounds include ethylenimine, azirine, azetidine, azete, pyrrolidine, pyrrole, piperidine, pyridine, hexamethyleneimine, azatropilidene, imidazole, pyrazole, oxazole, imidazoline, pyrazine, morpholine, pteridine, purine, and the like. Compounds having these skeletons attached to an amino group or methyl group may be used. Among these, heterocyclic compounds having a 5 to 7-membered ring containing carbon, or an oxygen as a heteroatom and carbon, and having one or two nitrogen atoms as heteroatoms in the ring constituent atoms. Examples include pyrrolidine, pyrrole, piperidine, pyridine, hexamethyleneimine, azatropilidene, imidazole, pyrazole, oxazole, imidazoline, pyrazine, morpholine, and like compounds, as well as a group of compounds having the cyclic skeleton as a basic structure. Further, compounds having a multiple polycyclic structure with 4 or more nitrogen heteroatoms, such as purine, pteridine, and like compounds, and a group of compounds having such a multiple polycyclic structure as a basic structure are also preferable. Among these, compounds having a 5 to 6-membered ring are preferable. Examples include pyrrolidine, pyrrole, piperidine, pyridine, imidazole, pyrazole, oxazole, imidazoline, pyrazine, morpholine, and like compounds, as well as a group of compounds having the cyclic skeleton as a basic structure. Among these, pyrrole, pyridine, imidazole, pyrazole, oxazole, imidazoline, pyrazine, and like compounds having a double bond in the ring, and a group of compounds having the cyclic skeleton as a basic structure are particularly preferable. Examples of substituents constituting these group of compounds include amino group, methyl group and the like. Compounds in which these substituents are attached may also be used. Particularly preferred are 2-aminopyridine, 4-aminopyridine, and like aminopyridine, and 2-methylimidazole and like methylimidazole. Most preferred are pyridine, imidazole, aminopyridine, methylimidazole and the like.

Particularly preferable examples of nitrogen-containing heterocyclic compound are pyridine; 2-aminopyridine, 4-aminopyridine, and like aminopyridine; imidazole; 2-methylimidazole and like methylimidazole; pyrazole; pteridine; oxazole, and the like.

The pH buffer may be used alone or as a mixture of two or more kinds.

The concentration of the pH buffer in the sealing treatment solution is preferably, but not particularly limited to, 0.1 to 100 g/L, and more preferably 0.2 to 20 g/L. With this range of concentration of the pH buffer, the sealing treatment solution exerts a superior pH buffering property; further, undesirable appearance (stains after drying) of the treated product surface due to excessively-high concentration of the pH buffer or uneven coloring of colored products may be suppressed.

Surfactant

The surfactant is not particularly limited and previously known surfactants may be used. Examples of such surfactants include anionic surfactants, nonionic surfactants, and ampholytic surfactants.

Examples of anionic surfactants include sulfate-based surfactants, sulfonate-based surfactants, and phosphorus-based surfactants.

Examples of sulfate-based surfactants include aromatic sulfate-based surfactants, aliphatic sulfate-based surfactants, and the like.

Examples of aromatic sulfate-based surfactants include polyoxyethylene alkylphenyl ether sulfate. Further, examples of aliphatic sulfate-based surfactants include polyoxyethylene alkyl ether sulfate.

Examples of sulfonate-based surfactants include aromatic sulfonate-based surfactants.

Examples of aromatic sulfonate-based surfactants include benzenesulfonate, naphthalene sulfonate and like aromatic sulfonate-based surfactants; and compounds in which the aromatic sulfonate skeleton, such as benzenesulfonate or naphthalene sulfonate, is substituted with an alkyl group, polyoxyethylene group, polyoxyethylene alkyl ether group, carboxyl group, carbonyl group, hydroxyl group, alcohol group, vinyl group, allyl group, or like alkylene group or a multiple bond-containing group, or a further sulfonic acid group, as well as copolymers or polycondensates of the compound with formalin or the like. Examples of such aromatic sulfonate-based surfactants include alkylbenzene sulfonates, alkyl naphthalene sulfonates, and their formalin polycondensates, polycondensates of naphthalene sulfonate with formalin or the like, copolymers of alkylene benzene sulfonates or alkylene naphthalene sulfonates, and the like.

Examples of aromatic sulfonate-based surfactants include compounds in which a plurality of phenyl sulfonates are bonded through ether bond, such as diphenyl ether sulfonate or the like, as well as these compounds substituted with an alkyl group, polyoxyethylene group, polyoxyethylene alkyl ether group or the like. Examples of such aromatic sulfonate-based surfactants include alkyl diphenyl ether disulfonates, alkyl diphenyl ether disulfosuccinate, and the like.

Examples of phosphorus-based surfactants include phosphoric ester-based surfactants and salts of phosphoric ester-based surfactants, and the like. More specifically, examples include polyoxyethylene alkyl ether phosphoric ester, polyoxyethylene alkylene-substituted phenyl ether phosphoric ester, alkyl phosphoric ester, and the like, and salts thereof.

Examples of nonionic surfactants include nonionic surfactants capable of adjusting the concentration of the sealing treatment solution, and setting the cloud point in the sealing treatment solution to 85° C. or higher by being combined with other surfactants may preferably be used. Examples of such nonionic surfactants include polyoxyethylene alkyl ether, glycerin ester polyoxyethylene ether, sorbitan ester, fatty acid alkanol amide, and the like.

Examples of ampholytic surfactants include alkylbetaine, fatty acid amidebetaine, alkylamine oxide, and the like.

Among these surfactants, anionic surfactants are preferable. In particular, sulfate-based surfactants, sulfonate-based surfactants, and phosphorus-based surfactants are more preferable, and sulfonate-based surfactants are furthermore preferable.

The surfactant may be used alone or as a mixture of two or more kinds. A suitable nonionic surfactant that decreases the cloud point of the sealing treatment solution is selected. Further, by mixing a nonionic surfactant and an anionic surfactant, the cloud point of the surfactant may be increased. When an anionic surfactant is used, a suitable anionic surfactant that does not cause turbidity by being reacted with the metal contained or an ampholytic surfactant is selected.

The concentration of the surfactant in the sealing treatment solution is not particularly limited, and preferably 10 mg/L to 10 g/L, more preferably 20 mg/L to 5 g/L. The above range of surfactant concentration enables the sealing treatment solution to exert a sufficient sealing performance and inhibit a dusty surface or undesirable foggy appearance of the sealed anodic oxide film.

pH Adjuster

The sealing treatment solution of the present invention may further contain a pH adjuster. The pH adjuster is not particularly limited and any previously known pH adjusters may be used.

Examples of a pH adjuster to adjust the sealing treatment solution to be more acidic include dilute aqueous solutions of acetic acid, sulfamic acid, sulfuric acid, nitric acid, organic sulfonic acid, and the like. Of these, nitric acid is preferable in terms of a superior sealing performance.

Examples of a pH adjuster to adjust the sealing treatment solution to be more alkaline include aqueous ammonia, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and the like. Of these, sodium hydroxide aqueous solution is preferable in terms of a superior sealing performance.

The pH adjuster may be used alone or as a mixture of two or more kinds.

The concentration of the pH adjuster in the sealing treatment solution is preferably, but not particularly limited to, 0 to 20 g/L, more preferably 0 to 10 g/L and furthermore preferably 0 to 5 g/L. With this range of concentration of the pH adjuster, the sealing treatment solution exerts a sufficient sealing performance; further, it is possible to inhibit a decrease in the sealing degree of the anodic oxide film sealed by the sealing treatment solution.

Other Components

The sealing treatment solution of the present invention may contain, as necessary, mildew-proofing agents, complexing agents, and other additives, so as to improve the sealing performance and the practical utility of the solution. Examples of additives include benzoic acid, benzoate, and like mildew-proofing agents; and citric acid, citrate and like complexing agents. Further, a commercially available mildew-proofing agent, for example, “TAC Kabikoron” (Okuno Chemical Industries Co., Ltd.) may be added.

Sealing Treatment Solution

In the sealing treatment solution of the present invention, the total amount of the metal salt, the pH buffer, and the surfactant is 0.2 to 100 g/L, preferably 0.3 to 50 g/L, and more preferably 0.5 to 30 g/L. The above range of the total amount enables the sealing treatment solution to exert a sufficient sealing performance, enables the anodic oxide film of aluminum alloy sealed by the sealing treatment solution to exert a sufficient contamination resistance, and inhibits a dusty surface or undesirable foggy appearance of the sealed anodic oxide film.

The pH of the sealing treatment solution is preferably 7.0 to 10.0, more preferably 7.2 to 9.5, and furthermore preferably 7.5 to 9.0. Such a pH range enables the sealing treatment solution to exert a sufficient sealing performance, enables the anodic oxide film of aluminum alloy sealed by the sealing treatment solution to exert a sufficient contamination resistance, and inhibits an undesirable appearance due to the attachment of powdery substances to the surface of the treated product (dusty or foggy surface).

The other components of the sealing treatment solution of the present invention are not particularly limited insofar as the sealing treatment solution contains a metal salt, a pH buffer, and a surfactant. However, the sealing treatment solution is preferably an aqueous solution containing the components stated above.

The sealing treatment solution of the present invention is preferably free of nickel-based metal salt or like metal salt. Examples of such a metal salt include Ni, Co, Fe, Cr and the like.

2. Concentrated Liquid

The concentrated liquid of the present invention is a concentrated liquid of a sealing treatment solution for an anodic oxide film of aluminum alloy, and comprises a metal salt, a pH buffer, and a surfactant. The metal salt is at least one member selected from alkali metal salts and alkaline-earth metal salts. By preparing a concentrated liquid that contains high concentrations of the respective components of the sealing treatment solution, the liquid may be easily carried and stored. By diluting the liquid with water or a like diluent, the sealing treatment solution may be easily prepared. The diluent is preferably water.

The same metal salt, pH buffer, and surfactant contained in the sealing treatment solution may be used for the concentrated liquid of the present invention. Although the concentrated liquid of the present invention contains the same components as those of the sealing treatment solution, the contents of the components are different.

The total amount of the metal salt, pH buffer, and surfactant in the concentrated liquid is preferably 1 to 800 g/L, more preferably 1.5 to 400 g/L, and furthermore preferably 2.5 to 250 g/L. With this total amount range of the components in the concentrated liquid, the liquid may be easily carried and stored. Further, by diluting the liquid with water or a like diluent, the sealing treatment solution may be easily prepared. Further, the total amount of the metal salt, the pH buffer, and the surfactant in the concentrated liquid may be more than 100 g/L, or 150 g/L or more, so as to differentiate the concentrated liquid from the sealing treatment solution.

3. Sealing Treatment Method

The sealing treatment method of the present invention is a sealing treatment method for an anodic oxide film of aluminum alloy, the method comprising a step of immersing an article having an anodic oxide film of aluminum alloy in a sealing treatment solution for anodic oxide film of aluminum alloy, which comprises a metal salt, a pH buffer, and a surfactant. The metal salt is at least one member selected from alkali metal salts and alkaline-earth metal salts.

The sealing treatment solution described above may be used as the sealing treatment solution in this method. The sealing treatment method of the present invention comprises a step of immersing an article having an anodic oxide film of aluminum alloy in the sealing treatment solution. The immersion method is not particularly limited, and any previously known immersion method may be adopted.

The temperature of the sealing treatment solution in this step is preferably 85 to 100° C., more preferably 88 to 98° C., and furthermore preferably 90 to 98° C. The above temperature range of the sealing treatment solution ensures a sufficient sealing performance.

The pH of the sealing treatment solution is preferably 7.0 to 10.0, more preferably 7.2 to 9.5, and furthermore preferably 7.5 to 9.0. Such a pH range enables the sealing treatment solution to exert a sufficient sealing performance, and inhibits an undesirable appearance due to the attachment of powdery substances to the surface of the treated product (dusty or foggy surface).

The sealing treatment time is determined generally according to the thickness of the anodic oxide film to be treated. More specifically, the sealing treatment time is preferably a number (min) obtained by multiplying a number denoting the film thickness (μm) by 0.1 to 10, more preferably a number (min) obtained by multiplying a number denoting the film thickness (μm) by 0.2 to 5, and furthermore preferably a number (min) obtained by multiplying a number denoting the film thickness (μm) by 0.5 to 4. For example, if the thickness of the anodic oxide film is 10 μm, the immersion time is preferably about 2 to 50 minutes, which is obtained by multiplying 10 by 0.2 to 5. The above range of the sealing treatment time enables the sealing treatment solution to exert a sufficient sealing performance, enables the anodic oxide film of aluminum alloy sealed by the sealing treatment solution to exert a sufficient contamination resistance, and inhibits a decrease in the appearance of the treated object due to an undesirable appearance, such as a dusty or foggy surface.

In this step, the article having an anodic oxide film of aluminum alloy may be immersed in the sealing treatment solution while stirring the sealing treatment solution. Preferable examples of the stirring method include circulation stirring, air stirring, gas stirring, and rocking stirring. Among these, circulation stirring and gas stirring are preferable, and circulation stirring is more preferable. Preferable examples of gas stirring include gas stirring using nitrogen gas, argon gas, and like inert gases. In this step, when a sealing treatment solution containing Mg salt, Ca salt, Sr salt, Ba salt, and Ra salt as the metal salt and having a pH of 7 or more is used, the sealing treatment solution may absorb carbon dioxide in the air, thereby generating turbidity in some cases. Therefore, although circulation stirring is preferably used as a stirring method as stated above, if air stirring is required because of the facility, air stirring using an inert gas is preferable in terms of inhibiting the turbidity of the sealing treatment solution.

In the sealing treatment method of the present invention, a turbidity removal treatment for removing turbidity from the sealing treatment solution may be performed during the step of immersing an article having an anodic oxide film of aluminum alloy in the sealing treatment solution for anodic oxide film of aluminum alloy. Further, the turbidity removal treatment may also be performed at a time other than the above step, for example, during the standby time before the article is immersed in the sealing treatment solution for anodic oxide film or during the suspension of the line. By performing the turbidity removal treatment, it is possible to inhibit a decrease in the appearance of the anodic oxide film due to an undesirable appearance, such as a dusty or foggy surface.

The turbidity removal method is not particularly limited and any previously known removal methods may be used. Examples of the removal method include removal by filtration. More specifically, an example may be a filtration removal in which a part of the sealing treatment solution is supplied from a tank for performing the sealing treatment to a reserve tank, such as a cushion tank, which is a chemical supplying, adding, and dissolving tank. The sealing treatment solution is cooled to a temperature of, preferably, 50° C. or less, filtration is performed through a filter, and the filtrate is returned to the tank for performing the sealing treatment for circulation. If the facility does not have a cushion tank, the filtration removal may be performed by simple filtration circulation.

In the sealing treatment method of the present invention, the object to be treated is an anodic oxide film of aluminum alloy. The anodic oxide film of aluminum alloy is not particularly limited, and any anodic oxide films of aluminum alloy obtained by applying a known anodization method using sulfuric acid, oxalic acid, or the like to a general aluminum alloy may be used. The aluminum alloy is not particularly limited, and various aluminum-based alloys may be used as the object of the anodization. Specific examples of aluminum alloy include various aluminum-based alloy groups, typified by wrought aluminum alloys represented by JIS-A 1000s to 7000s, and cast materials and die-cast materials represented by AC, ADC, etc., specified by JIS.

Examples of anodization method to be applied to an aluminum alloy include a method of performing electrolysis using an aqueous solution having a sulfuric acid concentration of about 100 g/L to 400 g/L under a liquid temperature of about −10 to 30° C. at an anodic current-density of about 0.5 to 4 A/dm².

Further, in the sealing treatment method of the present invention, a film obtained by subjecting an anodic oxide film of aluminum alloy to electrolytic coloring may be treated.

The electrolytic coloring may be performed by a known coloring technique. For example, after the anodization is performed, the film may be immersed in an electrolytic coloring bath, followed by secondary electrolysis, thereby coloring the anodic oxide film. Examples of an electrolytic coloring bath include a nickel salt-boric acid bath, nickel salt-tin salt-sulfuric acid bath, and the like.

Further, in the sealing treatment method of the present invention, a film obtained by subjecting an anodic oxide film of aluminum alloy to coloring using a dye may be treated.

Examples of dyeing methods using a dye include a previously known method of immersing an anodic oxide film in an aqueous solution of a dye. Examples of such a dye include commercially available dye for use on an anodic oxide film of aluminum alloy, such as anionic dye and the like. The temperature of the aqueous solution of a dye is preferably 10 to 70° C., and more preferably 20 to 60° C. Further, the concentration of the dye in the dye aqueous solution and the immersion time may be appropriately set according to the desired color tone of the dye, desired color density, and the like.

When a film obtained by subjecting an anodic oxide film of aluminum alloy to coloring using a dye is treated and if the sealing treatment solution is incapable of imparting the dye fixing property, a dye fixing treatment may be performed after the coloring and before the sealing treatment. Examples of the dye fixing treatment agent to be used for the dye fixing treatment include commercially available agents for use in dyeing of anodic oxide films of aluminum alloy (e.g., TAC BONDING AGENT-2, TAC SUN BLOCK 77-5C, etc.; produced by Okuno Chemical Industries Co., Ltd.). Further, by adjusting the types and the compounding of the pH buffer and the surfactant in the sealing treatment solution, it is possible to impart a dye fixing property to the sealing treatment solution.

The sealing treatment method of the present invention may be performed by using an article having an anodic oxide film of aluminum alloy described above as an article to be treated, and immersing the article in the sealing treatment solution described above. Further, as necessary, it is also possible to subject the article having an anodic oxide film of aluminum alloy to electrolytic coloring, dye coloring, or the like, then sufficiently wash the article with water, and then immerse the article in the sealing treatment solution. This method greatly improves the sealing performance for the anodic oxide film of aluminum alloy of the object to be treated.

EXAMPLES

The present invention is more specifically described below with reference to Examples and Comparative Examples. However, the present invention is not limited to the Examples.

According to the following production conditions, anodized aluminum alloy test specimens were prepared to be used for the Examples and Comparative Examples below.

Preparation of Anodized Test Specimen A (without Dyeing Treatment and Dye Fixing Treatment)

An aluminum test specimen (JIS A1050P plate material) was degreased by being immersed in a weak alkaline degreasing agent (30 g/L aqueous solution of Top Alclean 101 (product name); produced by Okuno Chemical Industries Co., Ltd., bath temperature: 60° C.) for 3 minutes, followed by washing with water, and anodization was performed in an anodization bath containing sulfuric acid as a major component (containing 180 g/L of liberated sulfuric acid and 8.0 g/L of dissolved aluminum) (bath temperature: 20±1° C., anodic current-density: 1 Å/dm², electrolysis time: 30 minutes, film thickness=about 10 μm). The obtained anodic oxide film was washed with water, thereby obtaining an anodized aluminum alloy test specimen (hereinafter referred to as “anodized test specimen A”).

Preparation of Anodized Test Specimen B (with Dyeing Treatment and Dye Fixing Treatment)

An aluminum test specimen (JIS A1050P plate material) was degreased by being immersed in a weak alkaline degreasing agent (30 g/L aqueous solution of Top Alclean 101 (product name); produced by Okuno Chemical Industries Co., Ltd., bath temperature: 60° C.) for 3 minutes, followed by washing with water, and anodization was performed in an anodization bath containing sulfuric acid as a major component (containing 180 g/L of liberated sulfuric acid and 8.0 g/L of dissolved aluminum) (bath temperature: 20±1° C., anodic current-density: 1 A/dm², electrolysis time: 30 minutes, film thickness=about 10 μm). The obtained anodic oxide film was washed with water, and immersed in an acid activation bath containing 100 mL/L of 98% sulfuric acid (bath temperature: room temperature) for 1 minute for acid activation, followed by washing with water. Subsequently, a dyeing treatment was performed by immersing the test specimen in a dyeing treatment solution (TAC dye TAC BLACK 402 1 g/L; produced by Okuno Chemical Industries Co., Ltd.) for 1 minute at 50° C., followed by washing with water. Subsequently, a dye fixing treatment was performed by immersing the film in a dye fixing treatment solution (TAC BONDING AGENT-2 (product name) 20 mL/L; produced by Okuno Chemical Industries Co., Ltd) for 3 minutes at room temperature, followed by washing with water, thereby obtaining an anodized and dyed aluminum alloy test specimen (hereinafter referred to as “anodized test specimen B”).

Preparation of Anodized Test Specimen C (with Dyeing Treatment and without Dye Fixing Treatment)

An aluminum test specimen (JIS A1050P plate material) was degreased by being immersed in a weak alkaline degreasing agent (30 g/L aqueous solution of Top Alclean 101 (product name); produced by Okuno Chemical Industries Co., Ltd., bath temperature: 60° C.) for 3 minutes, followed by washing with water, and anodization was performed in an anodization bath containing sulfuric acid as a major component (containing 180 g/L of liberated sulfuric acid and 8.0 g/L of dissolved aluminum) (bath temperature: 20±1° C., anodic current-density: 1 A/dm², electrolysis time: 30 minutes, film thickness=about 10 μm). The obtained anodic oxide film was washed with water, and immersed in an acid activation bath containing 100 mL/L of 98% sulfuric acid (bath temperature: room temperature) for 1 minute for acid activation, followed by washing with water. Subsequently, a dyeing treatment was performed by immersing the test specimen in a dyeing treatment solution (TAC dye TAC BLACK 402 1 g/L; produced by Okuno Chemical Industries Co., Ltd.) for 1 minute at 50° C., followed by washing with water, thereby obtaining an anodized and dyed aluminum alloy test specimen (hereinafter referred to as “anodized test specimen C”).

Example 1

The anodized test specimen A produced according to the production conditions specified above was immersed in a sealing treatment solution (bath temperature: 92° C.) containing, as a metal salt, 1 g/L of sodium acetate, as a pH buffer, 1 g/L of ammonium acetate, and, as a surfactant, 0.5 g/L of sodium naphthalene sulfonate formalin polycondensation product, adjusted in pH by nitric acid and aqueous ammonia to 7.0, 8.0, or 9.0, for minutes, 10 minutes, or 20 minutes for each pH, thereby performing a sealing treatment.

Example 2

A sealing treatment was performed in the same manner as in Example 1, except that anodized test specimen B was used.

Example 3

A sealing treatment was performed in the same manner as in Example 1, except that a sealing treatment solution, which is an aqueous solution containing, as a metal salt, 5 g/L of magnesium acetate, as a pH buffer, 0.5 g/L of triethanolamine, and, as a surfactant, 0.2 g/L of sodium dodecylbenzene sulfonate, adjusted in pH by acetic acid and sodium hydroxide, was used.

Example 4

A sealing treatment was performed in the same manner as in Example 1, except that a sealing treatment solution, which is an aqueous solution containing, as a metal salt, 5 g/L of calcium nitrate, as a pH buffer, 4 g/L of alanine, and, as a surfactant, 0.2 g/L of alkylene phenyl sodium sulfonate copolymerization product, adjusted in pH by nitric acid and aqueous ammonia, was used.

Example 5

A sealing treatment was performed in the same manner as in Example 1, except that a sealing treatment solution, which is an aqueous solution containing, as a metal salt, 10 g/L of magnesium nitrate, as a pH buffer, 4 g/L of pyridine, and, as a surfactant, 0.5 g/L of sodium naphthalene sulfonate formalin polycondensation product, adjusted in pH by nitric acid and potassium hydroxide, was used.

Example 6

A sealing treatment was performed in the same manner as in Example 1, except that anodized test specimen B and a sealing treatment solution, which is an aqueous solution containing, as a metal salt, 10 g/L of magnesium nitrate, as a pH buffer, 4 g/L of pyridine, and 0.5 g/L of sodium naphthalene sulfonate formalin polycondensation product, adjusted in pH by nitric acid and potassium hydroxide, were used.

Example 7

The anodized test specimen A produced according to the production conditions specified above was immersed in a sealing treatment solution (bath temperature: 92° C.), which is an aqueous solution containing, as a metal salt, 10 g/L of potassium nitrate, as a pH buffer, 0.5 g/L of 2-aminopyridine and 0.5 g/L of 2-methylimidazole, and, as a surfactant, 0.2 g/L of polyoxyethylene styrenated phenyl ether phosphoric ester, adjusted in pH by nitric acid and aqueous ammonia to 7.5 or 9.5, for 5 minutes or 20 minutes for each pH, thereby performing a sealing treatment.

Example 8

A sealing treatment was performed in the same manner as in Example 7, except that a sealing treatment solution, which is an aqueous solution containing, as a metal salt, 20 g/L of magnesium nitrate, as a pH buffer, 0.5 g/L of 2-aminopyridine and 0.5 g/L of 2-methylimidazole, and, as a surfactant, 0.2 g/L of polyoxyethylene styrenated phenyl ether phosphoric ester, adjusted in pH by nitric acid and aqueous ammonia, was used.

Example 9

A sealing treatment was performed in the same manner as in Example 7, except that anodized test specimen B and a sealing treatment solution, which is an aqueous solution containing, as a metal salt, 1 g/L of barium nitrate, as a pH buffer, 1 g/L of pyrazole and 1 g/L of pteridine, and, as a surfactant, 1 g/L of fatty acid amide alkyl betaine and 0.2 g/L of alkylene phenyl sodium sulfonate copolymerization product, adjusted in pH by nitric acid and aqueous ammonia, were used.

Example 10

A sealing treatment was performed in the same manner as in Example 7, except that anodized test specimen A and a sealing treatment solution, which is an aqueous solution containing, as a metal salt, 20 g/L of magnesium nitrate, as a pH buffer, 2 g/L of imidazole, and, as a surfactant, 0.1 g/L of sodium polyoxyethylene alkyl ether sulfate and 0.2 g/L of sodium polyoxyethylene phenyl ether sulfate, adjusted in pH by nitric acid and aqueous ammonia, were used.

Example 11

A sealing treatment was performed in the same manner as in Example 7, except that anodized test specimen A and a sealing treatment solution, which is an aqueous solution containing, as a metal salt, 20 g/L of magnesium nitrate, as a pH buffer, 2 g/L of imidazole, and, as a surfactant, 0.01 g/L of polyoxyethylene alkyl ether and 0.2 g/L of alkylene phenyl sodium sulfonate copolymerization product, adjusted in pH by nitric acid and aqueous ammonia, were used.

Example 12

A sealing treatment was performed in the same manner as in Example 7, except that anodized test specimen B and a sealing treatment solution, which is an aqueous solution containing, as a metal salt, 5 g/L of calcium nitrate, as a pH buffer, 1 g/L of oxazole, and, as a surfactant, 0.2 g/L of fatty acid amide alkyl betaine and 0.5 g/L of sodium dodecylbenzene sulfonate, adjusted in pH by nitric acid and aqueous ammonia, were used.

Comparative Example 1

A sealing treatment was performed by immersing anodized test specimen A in boiling water (ion exchanged water) at 92° C. for 20 minutes.

Comparative Example 2

A sealing treatment was performed by immersing anodized test specimen A in a sealing treatment solution (bath temperature: 92° C.) constituted of an aqueous solution containing 40 mL/L of nickel acetate-based sealing agent (Top Seal H-298 (product name); produced by Okuno Chemical Industries Co., Ltd.) having a pH of 5.6 for 5 minutes, 10 minutes, or 20 minutes.

Comparative Example 3

A sealing treatment was performed in the same manner as in Comparative Example 2, except that anodized test specimen C was used.

Comparative Example 4

A sealing treatment was performed in the same manner as in Example 7, except that a sealing treatment solution, which is an aqueous solution containing 10 g/L of ammonium sulfate, as a pH buffer, 0.5 g/L of 2-aminopyridine and 0.5 g/L of 2-methylimidazole, and, as a surfactant, 0.2 g/L of polyoxyethylene styrenated phenyl ether phosphoric ester, adjusted in pH by nitric acid and aqueous ammonia, was used.

In the above Examples and Comparative Examples, immediately after the anodized test specimens were subjected to a sealing treatment, the test specimens were washed with running tap water for 1 minute. Subsequently, after each anodized test specimen was dried using a dryer, the test specimen was allowed to stand overnight at room temperature, thereby preparing a sealed anodized test specimen.

The sealed anodized test specimens prepared in the above Examples and Comparative Examples were evaluated using the following test method.

Sealing Degree

According to JIS H 8683-2:1999 (sealing degree test method for an anodic oxide film of aluminum or aluminum alloy, Part 2: phosphoric acid-chromic acid aqueous solution immersion test), each of the sealed test specimen was immersed in a phosphoric acid-chromic acid aqueous solution, thereby measuring a decrease in mass of the test specimen per unit area. A smaller value indicates a superior sealing degree.

Contamination Resistance (Magic Marker Test-Stain Removal Property Test)

Each of the sealed test specimens was allowed to stand for a day at room temperature, and a mark was made on its surface with an oil-based black magic marker, followed by still standing for 30 seconds. Subsequently, the test specimen was wiped with a boxed tissue soaked with water or isopropyl alcohol, and evaluated according to the following criteria.

⊚: The mark was completely removed by a gentle wipe. ◯: The mark was removed by a hard wipe. Δ: The mark slightly remained even after a hard wipe. x: The black color of the mark remained.

When the evaluation result was A grade in a test using water, it was evaluated that the contamination resistance was acceptable in practical use.

Appearance Evaluation

The presence or absence of a dusty or foggy surface, or the resulting generation of an interference film rainbow of the sealed anodized test specimen was confirmed by visual inspection, and evaluation was performed according to the following criteria.

⊚: The dusty or foggy surface, or resulting generation of an interference film rainbow was not observed at all and the appearance was excellent. ◯: The dusty or foggy surface, or resulting generation of an interference film rainbow was slightly observed; however, the appearance was at an acceptable level. Δ: The dusty or foggy surface, or resulting generation of an interference film rainbow was observed and the appearance was slightly inferior. x: Significant dusty or foggy surface, and resulting significant generation of an interference film rainbow were observed and the appearance was severely inferior.

Tables 1 to 5 show the results.

TABLE 1 Sealing Sealing Contamination Sealing Test Time Degree Resistance Treatment Solution Specimen pH (min) (mg/dm²) Alcohol Water Appearance Example 1 Sodium Acetate A 7.0 5 24.5 ◯ Δ ⊚ Ammonium Acetate 10 15.7 ◯ Δ ⊚ Sodium Naphthalene 20 10.3 ⊚ Δ ◯ Sulfonate Formalin 8.0 5 23.7 ◯ Δ ⊚ Polycondensation 10 12.8 ◯ Δ ⊚ Product 20 9.5 ⊚ ◯ ◯ 9.0 5 22.6 ◯ Δ ⊚ 10 12.1 ⊚ Δ ◯ 20 8.8 ⊚ ◯ ◯ Example 2 Sodium Acetate B 7.0 5 24.7 ◯ Δ ⊚ Ammonium Acetate 10 16.2 ◯ Δ ◯ Sodium Naphthalene 20 10.0 ⊚ Δ ◯ Sulfonate Formalin 8.0 5 22.7 ◯ Δ ⊚ Polycondensation 10 13.1 ◯ Δ ◯ Product 20 9.9 ⊚ ◯ ◯ 9.0 5 22.4 ◯ Δ ⊚ 10 12.5 ⊚ Δ ◯ 20 9.2 ⊚ ◯ ◯ Example 3 Magnesium Acetate A 7.0 5 21.8 ◯ Δ ⊚ Triethanolamine 10 9.7 ⊚ ◯ ⊚ Sodium 20 4.4 ⊚ ⊚ ◯ Dodecylbenzene 8.0 5 19.5 ◯ Δ ⊚ Sulfonate 10 7.8 ⊚ ◯ ⊚ 20 3.7 ⊚ ⊚ ◯ 9.0 5 17.2 ◯ Δ ⊚ 10 5.6 ⊚ ⊚ ◯ 20 2.8 ⊚ ⊚ ◯

TABLE 2 Sealing Sealing Contamination Sealing Test Time Degree Resistance Treatment Solution Specimen pH (min) (mg/dm²) Alcohol Water Appearance Example 4 Calcium Nitrate A 7.0 5 24.3 ◯ Δ ⊚ Alanine 10 11.4 ⊚ ◯ ⊚ Alkylene Phenyl 20 8.0 ⊚ ◯ ⊚ Sodium 8.0 5 22.7 ◯ Δ ⊚ Sulfonate 10 10.5 ⊚ ◯ ⊚ Copolymerization 20 5.1 ⊚ ⊚ ◯ Product 9.0 5 20.4 ◯ Δ ⊚ 10 8.2 ⊚ ◯ ⊚ 20 4.3 ⊚ ⊚ ◯ Example 5 Magnesium Nitrate A 7.0 5 17.6 ◯ Δ ⊚ Pyridine 10 8.8 ⊚ ◯ ⊚ Sodium 20 4.1 ⊚ ⊚ ⊚ Naphthalene 8.0 5 15.5 ⊚ Δ ⊚ Sulfonate 10 5.4 ⊚ ⊚ ⊚ Formalin 20 3.2 ⊚ ⊚ ⊚ Polycondensation 9.0 5 11.2 ⊚ ◯ ⊚ Product 10 4.5 ⊚ ⊚ ⊚ 20 2.2 ⊚ ⊚ ◯ Example 6 Magnesium Nitrate B 7.0 5 17.4 ◯ Δ ⊚ Pyridine 10 9.2 ⊚ ◯ ⊚ Sodium 20 4.0 ⊚ ⊚ ⊚ Naphthalene 8.0 5 15.9 ⊚ Δ ⊚ Sulfonate 10 5.2 ⊚ ⊚ ⊚ Formalin 20 3.5 ⊚ ⊚ ◯ Polycondensation 9.0 5 11.4 ⊚ ◯ ⊚ Product 10 4.6 ⊚ ⊚ ◯ 20 2.5 ⊚ ⊚ ◯

TABLE 3 Sealing Sealing Contamination Sealing Test Time Degree Resistance Treatment Solution Specimen pH (min) (mg/dm²) Alcohol Water Appearance Comparative Boiling Water A — 20 46.7 Δ X X Example 1 Comparative Nickel A 5.6 5 18.9 ◯ Δ ⊚ Example 2 Acetate-based 10 7.4 ⊚ ◯ ⊚ Top Seal H- 20 2.7 ⊚ ⊚ ⊚ 298 Comparative Nickel C 5.6 5 19.5 ◯ Δ ⊚ Example 3 Acetate-based 10 7.8 ⊚ ◯ ⊚ Top Seal H- 20 3.1 ⊚ ⊚ ◯ 298

TABLE 4 Sealing Sealing Contamination Sealing Test Time Degree Resistance Treatment Solution Specimen pH (min) (mg/dm²) Alcohol Water Appearance Example 7 Potassium Nitrate A 7.5 5 19.4 ◯ Δ ⊚ 2-aminopyridine 20 10.2 ⊚ ◯ ◯ 2-methylimidazole 9.5 5 17.2 ◯ Δ ⊚ Polyoxyethylene 20 6.2 ⊚ ⊚ ◯ Styrenated Phenyl Ether Phosphoric ester Example 8 Magnesium Nitrate A 7.5 5 16.5 ◯ Δ ⊚ 2-aminopyridine 20 4.4 ⊚ ⊚ ◯ 2-methylimidazole 9.5 5 11.0 ⊚ ◯ ⊚ Polyoxyethylene 20 2.6 ⊚ ⊚ ◯ Styrenated Phenyl Ether Phosphoric ester Example 9 Barium Nitrate B 7.5 5 17.2 ◯ Δ ⊚ Pyrazole, Pteridine 20 5.4 ⊚ ⊚ ⊚ Fatty Acid Amide 9.5 5 12.3 ⊚ ◯ ⊚ Alkyl Betaine 20 4.2 ⊚ ⊚ ⊚ Alkylene Phenyl Sodium Sulfonate Copolymerization Product Example 10 Magnesium Nitrate A 7.5 5 16.3 ◯ Δ ⊚ Imidazole 20 4.5 ⊚ ⊚ ⊚ Sodium Polyoxy- 9.5 5 11.4 ⊚ ◯ ⊚ ethylene Alkyl Ether 20 2.5 ⊚ ⊚ ◯ Sulfate Sodium Polyoxy- ethylene Phenyl Ether Sulfate Example 11 Magnesium Nitrate A 7.5 5 15.0 ⊚ ◯ ⊚ Imidazole 20 4.1 ⊚ ⊚ ⊚ Polyoxyethylene 9.5 5 10.4 ⊚ ◯ ⊚ Alkyl Ether 20 2.2 ⊚ ⊚ ⊚ Alkylene Phenyl Sodium Sulfonate Copolymerization Product Example 12 Calcium Nitrate B 7.5 5 18.0 ◯ Δ ⊚ Oxazole 20 5.5 ⊚ ⊚ ◯ Fatty Acid Amide 9.5 5 15.7 ⊚ Δ ⊚ Alkyl Betaine 20 3.8 ⊚ ⊚ ◯ Sodium Dodecylbenzene Sulfonate

TABLE 5 Sealing Sealing Contamination Sealing Test Time Degree Resistance Treatment Solution Specimen pH (min) (mg/dm²) Alcohol Water Appearance Comparative Ammonium Sulfate A 7.5 5 29.5 Δ X ⊚ Example 4 2-aminopyridine 20 15.3 ◯ Δ ◯ 2-methylimidazole 9.5 5 25.0 Δ X ⊚ Polyoxyethylene 20 10.8 ⊚ Δ ◯ Styrenated Phenyl Ether Phosphoric ester

As is clearly shown in Tables 1 to 5, by using the sealing treatment solutions of Examples 1 to 12, a sealing performance comparative to that in the case using a sealing treatment solution containing a nickel salt was ensured, even though a sealing treatment solution free of a nickel salt was used. Further, it was revealed that, by using the sealing treatment solution of Examples 1 to 12, the anodic oxide film treated by the sealing treatment solution exhibited a superior contamination resistance.

Example 13

A sealing treatment was performed by immersing anodized test specimen A in 1 L of a sealing treatment solution (bath temperature: 92° C.), which is an aqueous solution containing, as a metal salt, 10 g/L of magnesium nitrate, as a pH buffer, 4 g/L of pyridine, and, as a surfactant, 0.5 g/L of sodium naphthalene sulfonate formalin polycondensation product, adjusted in pH to 9.0 by nitric acid and potassium hydroxide. More specifically, 20 test specimens were sequentially immersed in the sealing treatment solution under argon gas stirring, for 20 minutes for each test specimen. Each test specimen had a size of 5 cm×10 cm, and the total area of both surfaces was 1 dm².

Example 14

A sealing treatment was performed in the same manner as in Example 13, except that air stirring was performed instead of argon gas stirring.

Although the sealing bath became severely cloudy by air stirring in Example 14, the sealing bath became cloudy only slightly in Example 13 in which argon gas stirring was performed. Further, it was possible to remove the cloudy matter in Examples 13 and 14 by filtration removal. 

1-17. (canceled)
 18. A sealing treatment solution for anodic oxide film of aluminum alloy, the sealing treatment solution comprising a metal salt, a pH buffer, and a surfactant, the metal salt being at least one member selected from the group consisting of alkali metal salts and alkaline-earth metal salts, the pH buffer being a nitrogen-containing heterocyclic compound.
 19. The sealing treatment solution according to claim 18, wherein the metal salt is a metal salt of at least one metal selected from the group consisting of Na, Mg, K and Ca.
 20. The sealing treatment solution according to claim 18, wherein the metal salt is a metal salt of at least one metal selected from the group consisting of Mg and Ca.
 21. The sealing treatment solution according to claim 18, wherein the metal salt is at least one member selected from the group consisting of acetates, sulfamates, sulfates, and nitrates.
 22. The sealing treatment solution according to claim 18, wherein the metal salt is a nitrate.
 23. The sealing treatment solution according to claim 18, wherein the surfactant is at least one member selected from the group consisting of anionic surfactants and ampholytic surfactants.
 24. The sealing treatment solution according to claim 18, wherein the surfactant is at least one member selected from the group consisting of sulfate-based surfactants, sulfonate-based surfactants, and phosphoric ester-based surfactants.
 25. The sealing treatment solution according to claim 18, wherein the sealing treatment solution has a pH of 7.0 to 10.0.
 26. The sealing treatment solution according to claim 18, wherein the sealing treatment solution is free from nickel-based metal salt.
 27. The sealing treatment solution according to claim 18, wherein the total amount of the metal salt, the pH buffer, and the surfactant in the sealing treatment solution is 0.2 to 100 g/L.
 28. A concentrated liquid of a sealing treatment solution for anodic oxide film of aluminum alloy, the sealing treatment solution comprising a metal salt, a pH buffer, and a surfactant, the metal salt being at least one member selected from the group consisting of alkali metal salts and alkaline-earth metal salts, the pH buffer being a nitrogen-containing heterocyclic compound.
 29. A sealing treatment method for anodic oxide film of aluminum alloy, comprising the step of: immersing an article having an anodic oxide film of aluminum alloy in a sealing treatment solution for an anodic oxide film of aluminum alloy, the sealing treatment solution comprising a metal salt, a pH buffer, and a surfactant, and the metal salt being at least one member selected from the group consisting of alkali metal salts and alkaline-earth metal salts, the pH buffer being a nitrogen-containing heterocyclic compound.
 30. The sealing treatment method according to claim 29, wherein the sealing treatment solution has a liquid temperature of 85 to 100° C.
 31. The sealing treatment method according to claim 29, wherein the sealing treatment solution has a pH of 7.0 to 10.0.
 32. An article sealed by the sealing treatment method according to claim
 29. 